Blading for reaction turbines



March 4, 1930. J.. DE FREUDENREICH ET AL 1,749,523

BLADING FOR REACTION TURBINES Filed May 15, 1926 Fig.4.

Fig.2.

Patented Mar. 4, 1930 UNITED STATES.

PATENT OFFICE JE AN nu FREUDENREICH, OF IBADEN, AND KARL FREY, 0FENNETBADEN, SWITZER- LAND, ASSIGNORS TO AKTIENGESELLSCHAFT BROWN BOVERI& CIE., 0F BADEN,

SWITZERLAND, A JOINT-STOCK COMPANY OF SWITZERLAND.

BLADING non REACTION 'runnmns Application filed May 13,1926, Serial No.

This invention relates to the construction of turbines actuated byexpansion fluid, as ex-' amplified by steam turbines. It pertainsparticularly to steam turbines of the reaction type, and has to do withthe construction or arrangement of theblading for both or either thestator or rotor;

. The general object of the invention is the provision of a bladingarrangement for reaction turbines which will increase the powerefliciency of the engine.

Another object is the provision of a blading arrangement which will, inmany instances, permita reduction in the size of the machines.

Another objectis the provision of a construction which will reduce cost,by decreasing the number ofblades in a stage.

Other and further objects will be pointed out or indicated hereinafter,or will be obvious to one skilled in the art upon an understanding ofthe invention.

In the drawing forming a part of this specification we illustrate twodesigns embodying the present improvements, but the same are presentedfor the purpose of illustration only, and are not to be construed toimpose limitations on the claims short of thetrue and most comprehensivescope of the invention in the art.

In the drawing,

Fig. 1 is a diagrammatic illustration of a portion of a stage of bladingdemonstrative ot the invention, showing three blades each of adjacentstator and rotor rings, the blades being shown in section takenconcentrically I with the turbine axis.

Fig. 2 is a graph illustrating the relationship of parts of the bladeprofile. I

Fig. 3 is a section diagram of blading of the conventional Parsonsdesign.

. tures illustrated in Figs. 3 and 4.

Fig. 4 is a diagram of a blading profile demonstrative of the inventionin a. design differing from that of Fig. 1. v

Fig. 5 is a graph illustrating the relationship of certain parts of therespective struc- Heretofore in thedesigning oi reaction turbines, sofar as we have been able to ascertam,rap1d changes 1n the cross sectionand r The movin blades are desi 108,728, and in Switzerland May 27,1925.

direction of the flow of steam through the blading have been regarded asdisadvantageous, and consequently have been avoided, the designs havingbeen arranged to give the steam passages or channels between the bladesa form of gradually contracting contour free from abrupt change ofdirection. Moreover, it has been considered of importance to have thenarrower portion of the passage at the profile have shown, contrary tothe beliefs eretofore held, that the design and arrange-- ment ofblading which provides a steam passage Which is comparatively wide inthe portion adjacent the entrance side, and changes direction quitesharply, giving an acute'exit angle and having the narrow exit portionof the ath comparatively short, gives sub stantially increased powerefficiency, as well as various constructional advantages.

The nature of the invention may be ascertained by reference to thedrawing, wherein Fig. 1 illustrates a profile and arrangement of ourimproved blading, as applied to an axial-flow steam turbine. In thisfigure the upper row of blades, designated 10, repre sents-a section ofblading on a wheel or rotor of a reaction turbine, while the rowdesignated 11 represents a section of 'a portion of the adjacent rowoffixed blading. It is wellv to observe at this point that our newblading construction is equally ada ted for both moving and stationastages 0 reaction turbines, and that it can e employed to best advantagewhen utilized in both in conjunction. ated 12 and the secondary b ades13. It wil be observed that their form and arrangement are suchthat thesteam passage or channel between the blades exit side. This contractedexit portion of the passage, which we will designatethe velocityportion, is comparatively short in respect to both the total length ofthe passage and the exit portion of the previous standard design, whichis illustrated in Fig. 3. Thus the passage may be roughly apportioned asa pressure portion, which is relatively wide, an exit portion which isnarrow and quite short,

' and an intermediate contracting portion in which the direction of flowchanges rapidly. In the illustrated example the pressure por-' tion maybe regarded as the zone X, the intermediate portion as the zone Y andthe velocity portion as the zone Z. As a result ofthese particulars ofthe design, the change in direction of the flow passage is relativelyabrupt as compared with the previous design, resulting in the turning ofthe steam path to an acute exit angle in considerably shorter length. Inthe illustration given, the exit angle 1s approximately 18, which issuggested as re resenting an average between the limits of t e mostefiective arrangements,

exit angles varying between 16 and 20 hav- 1ng been found productive ofthe best effects. We have ascertained also that the rate of contractionin the width of the steam passage from the pressure portion to thevelocity portion may be determined and laid out in accordance with afairly accurate rule, of which the following method is an illustration.

- to the blade profiles, as shown in Fig. 1.

Let the line a in Fig. 2 represent the development of the median steampath a.w between the blades, and the cross sections 0, 1, 2, 3 .7,- setnp on the line a represent the radii of the correspondingly numberedcircles inscribed in the steam passage tangent With a properly chosenprofile the line (Z generated along the ends of the radii 0 shouldincline toward the line a at an angle of something over 15 throughoutthat portion representative of the intermediate zone Y. The end portionsof the line d will deviate from the intermediate portion, the part Zrepresenting the comparatively straight restricted velocity portion ofthe steam passage, while the part f represents the portions where theblades are rounded ed at entry in the example shown. It will beobservedin the example given that the portion Z represents only between onefourth to one fifth of the length of the entire path wa. An effectivedesign may also generate a line corresponding to the line d but curved,thechord of the intermediate portion being inclined at an angle of morethan 15 to the line a. In order that the condition for a rapid change ofthe passage width may be fulfilled, said curved line in the intermediateportion should be convex upwardly. If concave, it is a sign that thetransition will be gradual. The dotted curved in Fig. 2 is illustrativeof one form.

The novelty of this type of blade profile,

and the manner in which it differs from the usual standard reactionblading (Parsons), may be demonstrated by a comparison with a similaranalysis of the steam passage of the" latter. In Fig. 3 is shown adiagram of standard Parsons blading, and in Fig. 5 a diagrammaticanalysis of the same obtained by the method described above. It will beobserved that in this diagram the line 03, corresponding to the line dof Fig. 2', is concave upwardly in the intermediate portion and makes anangle of less than15 to the line a; The narrowest section Z comprises aconsiderably greater proportion of the line d, demonstrating that thelength of the contracted exit portion of the steam channel isconsiderably greater than is the case with profiles arranged accordingto the present invention.

While one advantage accruing from the present invention lies in the factthat it allows of a very small exit angle and a corresponding increasein the peripheral component of the steam force on the moving blades,with reduced frictional losses, improved power factor efficiencies maybe obtained by use of the invention in suitably designed blading inwhich the exit angle is greater than 20. In Fig. 4 is shown an exampleof such an arrangement, the profile being shaped in accordance with themethod described above, and illustrated by the line d in Fig. 5. Asdemonstrated by the analysis, this design presents a profile'frpm whichthe line (1'' is generated to extend through the greater proportion ofits length at an angle of more than 15 to the line a".

In the operation of the turbine, it is believed, the steam entering aring of rotary bladin exerts amomentary initial impulse on the ilades,following which the remaining kinetic energy of the steam becomesconverted into pressure which builds up in the pressure portion of thepassage. T e pressure, in turn, is transformed into kinetic en ergyagain in the velocity portion, exerting its reaction against the blades.drop incident to the development of the exit velocity is very rapid, sothat the reaction effect is very pronounced, and the friction losseslow, even with a small exit angle.

While one-of thegreat advantages of the invention as demonstrated bypractical use, is the increased power eflicienc obtained, which invarious instances has. een found to be as high as 6%, other importantand use- The heat ful results follow from the employment of theprinciples cha. \cterizing the invention. For example, it wn' beobserved that with the same circumferential pitch of thenew blading asemplgyed in the old, the width of the blades may be materially reduced.Likewise, thewidth of the stages may be substantially reduced.Furthermore, there may also be a reduction in the number of bladesrequired onv a given diameter. These various factors result in animportant decrease in the portions connecting through trance side and arelativellyl cost of manufacture, and it is believed, contributesomewhat to the strength and stability of the mounting of the blades. Asan example of a further development of the con-- struction disclosed,reference is made to our copending application Serial No. 206,491, filedJuly 18, 1927.

What we claim is 1. Reaction turbine blading comprising blades extendingradially and defining intervening steam passages,the blades having aprofile and arrangement giving said passages a relatively wide pressureportion at the enshort and ree exit side, said an intermediate portionof rapidly contracting width s'tricted velocity portion at t wherein theblade profile converges on the mean steam path of the passage at a rateelxceeding that of-the sides of an angle of 2. Reaction turbine bladinas specified in claim 1, wherein the intermediate portion of the steampassa e changes the direction of steam flow rapitfi 3. Reaction turliineblading as specified in claim 1, wherein the pressure portion of thesteam assage is longer, on the axial line of the tur ine, than is thevelocity portion.

4. Reaction turbine blading as specified in claim 1, wherein the lengthof the velocit portion is not over one fourth of the length of the totalmedian steam path. I,

5. Reaction turbine blading as specified in glaim '1, wherein the exitangle is less than 6. In a reaction turbine, the combination with arotary member, of reaction blades mounted thereon in ali nmentcircumferentially, said blades space to rovide intervening steam passaes, the bla e profile defining sa1d passages witli a relatively widepressure portion on the inlet side and a relatively narrow and shortvelocity portion on the exit Tide, said passage changing directionabrupty portion and its median line progressing throughout its lengthfrom. inlet to outlet in the direction counter to that of the bladesmovement.

7 Reaction turbine bladin blades extending radially an tervening steampassages, the blades having a profile and arrangement such that theencomprising from the pressure portlon to the veloclty' velope of aseries of circles inscribed in the passa e, when they are set up on astraight line 0 centers, converges for the greater part of its length onsaid line of centers at an angle in excess of 15.

8. In a fluid turbine, complementary blades spaced with respect to eachother to provide a fluid passage; the profile of adjacent faces of saidblades being such as to provide said passage at the entrance sidethereof with a relatlvely wide pressure portion, to provide said passageat the exit side thereof with a contracted veloclty portion relativelyshort as compared with the length of said passage, and to provide saidpassage intermediate said portions with a contracting portion angularlydisposed at all points with respect to said pressure portion m adirection counter to that of the blade movement to provide at suchintermediatecom .tractin portion for relatively rapid change portion andthe exit e rapidly contracting steam passages, each passage having awide pressure portion at the entry side, a short velocity portion at theexit side and a rapidly contracting accelerating portion between thepressure and velocity portions, the 'mean steam path in the pressure andacceleratlng portions bending continuously toward the exit side in thecircumferential direction of the row.

In testimony whereof we have hereunto subscribed our names at Zurich,Switzerland,

on the 27th day of. March, A. D. 1926.

- 7 JEAN ma FREUDENREIOH.

KARL FREY.

defining in a

